1. Field of the Invention
The invention relates to roller printing apparatuses, and in particular to a continuous roll-to-roll printing apparatuses.
2. Description of the Related Art
Conventional printing apparatuses can be categorized into sheet-to-sheet printing apparatuses and roll-to-roll printing apparatuses. FIG. 1 is a schematic diagram illustrating a conventional sheet-to-sheet printing apparatus. In FIG. 1, conventional sheet-to-sheet printing is performed by fixing a sheet substrate 15 on a printing stage 10. An alignment device 40 is used to align the sheet substrate 15 to the printing stage 10. The printing stage 10 with the sheet substrate 15 is then moved beneath the printing stencil 20. Paste 25 is transferred onto the sheet substrate 15 using a doctor blade 30 or squeegee. However, for conventional sheet-to-sheet printing, large scale printing cannot be achieved as it is a batch type printing method, wherein a single sheet of substrate is printed one at a time.
On the other hand, for a conventional continuous printing apparatus, skip printing methods are adopted to print a roll of continuous patterns for a planographic printing device. Skip printing methods are performed by sequentially printing 1st, 3rd, 5th . . . patterns. After the patterns are dried, 2nd, 4th, 6th . . . patterns are sequentially printed. Typically, the skip printing methods include two categories: one method includes: printing 1st, 3rd, 5th . . . patterns, drying the patterns, rewinding the roll of working pieces, and printing 2nd, 4th, 6th . . . patterns; the other method includes serially setting two sets of screen printing apparatuses and drying apparatuses, printing 1st, 4rd, 5th . . . patterns, drying the patterns, sequentially printing 2nd, 4th, 6th . . . patterns, and drying the patterns.
FIG. 2A is a schematic arrangement diagram illustrating a conventional roll-to-roll printing apparatus. In FIG. 2A, a roll-to-roll printing apparatus 100 includes a feeding machine 110 sending a flexible substrate roll to a statistic charge removing machine 120 and a first printing machine 130. Odd patterns 1P, 3P, 5P, 7P . . . (2n+1)P are printed (shown in FIG. 2B) on the flexible substrate roll and delivered to a UV drying machine 140. The flexible substrate roll is instantly delivered to a second printing machine. Even patterns 2P, 4P, 6P . . . (2n)P are printed (shown in FIG. 2B) on the flexible substrate and delivered to a UV drying machine 160. The flexible substrate is wound in a receiving machine 170.
The abovementioned first continuous printing method is advantageous in that apparatus costs and space required for the apparatus is minimal. However, different deformations between each winding process occur due to the flexible substrate being wound twice. Also, misplaced and superimposed patterns may be printed on the substrate due to the difficulty in printing subsequent patterns 2P, 4P, 6P on desired locations called stroke error. For the abovementioned second continuous printing method, it is advantageous in that tensile deformation is prevented due to the odd and even pattern process of the flexible substrate being performed under one tension.